1504
RALPH C. HUSTON AND JAMES A. HUTCHINSON
[CONTRIBUTION FROM
THE
VOl. 54
KEDZIECHEMICAL LABORATORY, MICHIGAN STATECOLLEGE ]
SOME MONO AND DIBROMO DERIVATIVES OF META-CRESOL BY RALPHC. HUSTON AND JAMES A. HUTCHINSON RECEIVEDOCTOBER 26, 1931
PUBLISHED APRIL6, 1932
The literature gives very little information concerning the bromine derivatives of m-cresol. Descriptions of the mono and dibromo derivatives are meager and often contradictory. In some cases definite proof of structure is entirely lacking. Because a more definite knowledge of these seemed desirable and because a knowledge of the structure of some of them was essential in determining the configuration of certain benzylated derivatives of m-cresol, the present study was undertaken. Monobromo-m-Cresols1 Direct Bromination.-One hundred and eight grams of purified m-cresol was dissolved in 200 cc. of chloroform, cooled to -10 and stirred continuously while 160 g. of bromine in 100 cc. of chloroform was added a t such a rate that the temperature did not a t any time exceed -5'. After all 'of the bromine had been added the stirring was continued for thirty minutes and the mixture was allowed to stand overnight. After several distillations, 26 g. came over a t 120-130", and 155 g. a t 130-140" (16 mm.). When repeatedly distilled a t atmospheric pressure (731 mm.), the 120-130" fraction came over a t 205-208 '. A sample dissolved in chloroform and treated with one molecular equivalent of bromine gave an excellent yield of 4,6-dibromo-3-methylphenol, which melted a t 65-66" and gave a benzoyl derivative melting a t 84-85' (see below). Anal. Calcd. for C7H70Br: Br, 42.78. Found: Br, 42.29. The 130-140 fraction solidified and was repeatedly crystallized from petroleum ether. It came down in long colorless silky needles which tended to mat together and melted a t 56-57 '. I n some cases it was crystallized from water. Anal. Calcd. for C7H70Br: Br, 42.78. Found: Br, 42.59, 42.65. Preparation of 6-Bromo-3-methylphenol from 4-Bromo-3-aminotoluene.-Acet-ptoluidide was nitrated2 and the acyl group removed by means of alcoholic potash. The amino group was replaced by bromine through the diazonium perbromide3 and the nitro group reduced by means of tin and hydrochloric acid to form 6-bromo-m-toluidine' melting a t 32-33' and boiling at 115-118' (16 mm.). The 6-bromo-m-toluidine was dissolved by boiling with dilute hydrochloric acid. When cooled the hydrochloride separated out. The mixture was cooled to O", and the calculated amount of sodium nitrite in water solution was added with constant stirring. After two hours the diazonium salt was decomposed by heating on the water-bath. Steam distillation gave a reddish-yellow oil. This was salted out and extracted with ether. After removal of the solvent the residue was treated with dilute sodium hydroxide and filtered. The filtrate was acidified with dilute hydrochloric acid, salted out and O,
O
Neville and Winther, Ber., 15, 2991 (1882); Walther and Zipper, J . prakt. Chem., [2] 91, 376 (1915); Hodgson and Moore, J. Chem. SOL, 2038 (1926); Hodgson and Beard, &id., 498 (1926); Darzens and Levy, Compl. rend., 193, 292 (1931). Gattermam, Ber., 18, 1483 (1885). Bulow and Schmactenberg, ibid., 41, 2609 (1908). *Neville and Winther, ibid., 13, 972 (1880); cf. Wroblewsky, Ann., 168, 177 (1873).
April, 1932
BROMO DERIVATIVES OF
rn-cmsoL
1505
extracted with ether, The 6-bromo-3-methylphenol obtained by distillation of the ether extract was proved by boiling point (206-208' a t 731 mm.), analysis, and bromination to 4,6-dibromo-3-methylphenolto be identical with the liquid monobromo-mcresol obtained by direct bromination. Preparation of 4-Bromo-3-methylphenol from Z-Bromo-S-aminotoluene.-Acetm-toluidine was brominated in acetic acid. The acyl group was removed and the 4bromo-m-toluidine crystallized from alcohol to a constant melting point of 79-80 '. The purified amine was dissolved in much dilute hydrochloric acid, cooled to 0 " and diazotized with the calculated amount of sodium nitrite. After two hours the diazonium salt was decomposed by heating on the water-bath, and steam distilled. The resulting yellow oil was salted out and extracted with ether. After purification of the crude phenol by dissolving in alkali, filtering and reprecipitating with acid, it was extracted with ether, and recrystallized from petroleum ether. It was identical in crystal form and melting point with the solid monobromo-m-cresol obtained by direct bromination. The yield was approximately 2570. Anal. Calcd. for C7H70Br: Br, 42.78. Found: Br, 42.72. Esters of 4-Bromo-3-methylphenol.-Benzoic, benzenesulfonic and p-toluenesulfonic esters were prepared from 4-bromo-3-methylphenol obtained both by direct bromination and by diazotization of 4-bromo-m-toluidine. The pyridine method was used.6
'
Benzoic ester Benzenesulfonic ester p-Toluenesulfonic ester
Crystal form (from alcohol)
M.p . , 'C.
Bromine, % Cslcd. Found
Fine white fluffy needles Long white needles Small lustrous plates
82.5-83 79-80 84-85
27.32 27.5 24.46 24.19 23.46 23.25
Dibromo-m-Cresols7 Direct Bromination.-One hundred and eight grams of m-cresol was brominated with 320 g. of bromine under the same experimental conditions as were used in the preparation of the monobromo-m-cresols. Upon distillation practically all of the product came over a t 130-140' (16 mm.) and solidified. Recrystallization from petroleum ether gave flat needles melting a t 64-65'. Evaporation of the mother liquor gave an oil which did not solidify at room temperature, and distilled at 132-135" (16 mm.). The crystalline compound was shown by analysis to be a dibromo-m-cresol. Anal. Calcd. for &HaOBrz: Br, 60.15. Found: Br, 59.93. Its sodium salt reacted with benzyl chloride in toluene to give an ortho benzyl derivative.* The benzoyl derivative, prepared by the pyridine method, crystallized from alcohol in mats of very fine needles melting a t 80-81 '. Anal. Calcd. for C14H1002Br2: Br, 43.2. Found: Br, 42.35. Since this phenol has an unsubstituted ortho position, it must be either 2,4-dibromo3-methylphenol or 4,6-dibromo-3-methylphenol. The oil (b. p. 132-135") obtained from the filtrates was seeded with a crystal of 4,6-dibromo-3-methylphenol prepared from the amine (see below). It solidified. After chilling it was pressed between pads of filter paper to remove oily impurities, and recrystallized from petroleum ether. Analysis, melting point (65-66') and melting point of the benzoyl derivative (84-85 ") proved it to be 4,6-dibromo-3-methylphenol. Neville and Winther, Ber., 13, 963 (1880). Einhorn and Holland, Ann., 301, 95 (1898). Gibbs and Robertson, J. Chem. SOC.,105, 1891 (1914); ibid., 105, 1888 (1914). * Huston and Houk, THISJOURNAL, 54,1606 (1932).
1506
RALPH C. HUSTON AND ALVA L. HOUK
Vol. 54
Anal. Calcd. for C7HeOBrz: Br, 60.15. Found: Br, 60.01. The less soluble phenol formed with it is therefore the 2,4-dibromo-3-methylphenol. Preparation of 4,6-Dibromll-3-rnethylphenol from 3-A~nino-4,6-dibromotoluene.Pure m-toluidine was acylated and treated in cold acetic acid solution with two molecular equivalents of bromine. The acyl group was removed by means of alcoholic potash, and the 4,6-dibromo-m-toluidine was recrystallized from alcohol to a constant melting point of 75-76 O.9 The purified amine was dissolved in hot, dilute hydrochloric acid, filtered and cooled to 0'. The calculated quantity of sodium nitrite was slowly added and the mixture was stirred until solution was complete. After two hours the diazonium salt was decomposed by heating on the water-bath and the dark colored mixture was steam distilled. The distillate was salted out and extracted with ether. After evaporation of the solvent the phenol was separated from the quinone by dissolving in dilute sodium hydroxide, reprecipitating with hydrochloric acid, and extracting with ether. The purified 4,6-dibromo-3-methylphenol crystallized from petroleum ether in fine flat crystals which cling to the sides of the beaker. The melting point (65-66 ") is ten degrees higher than that given by Gibbs and Robertson.' The benzoyl derivative came down from alcohol in fine needles melting at 84-85'. Anal. Calcd. for CI4H1~O2Br2: Br, 43.2. Found: Br, 43.78.
Summary Bromination of m-cresol in the cold with one molecular equivalent of bromine gave a mixture of 4-bromo-3-methylphenol and 6-bromo-3methylphenol. Bromination of m-cresol with two molecular equivalents of bromine gave a mixture of 2,4-dibromo-3-methylphenol and 4,6-dibromo-3-methylphenol. Neville and Winther, Ber., 13, 971 (1880). EASTLANSING, MICHIGAN [CONTRIBUTION FROM THE KEDZIECHEMICAL LABORATORY, MICHIGANSTATE COLLEGE]
ACTION OF AROMATIC ALCOHOLS ON AROMATIC COMPOUNDS IN THE PRESENCE OF ALUMINUM CHLORIDE. VIII. BENZYLATION OF META-CRESOL BY RALPH C. HUSTONAND ALVAL. HOUK RECEIVED OCTOBER 26, 1931
PUBLISHEDAPRIL6, 1932
This completes a series of three articles from this Laboratory on the benzylation of the cresols.' m-Cresol treated with benzyl alcohol and aluminum chloride in petroleum ether gave two monobenzyl cresols and one dibenzyl cresol: 3-methyl-4benzylpheno1,z 3-methyl-6-benzylphenol and 3-methyl-4,6-dibenzyIphenol. When treated with sodium and benzyl chloride in toluene (Claisen reaction)*it gave also two monobenzyl cresols and one dibenzyl cresol: 3-methyl2-benzylphenol, 3-methyl- 6 - benzylphenol and 3 -methyl-2,6 - dibenzylHuston and others, THISJOURNAL, 52, 4484 (1930); 53, 2379 (1931). Venturi, Gazz. chim. ital., 31, I, 472 (1901). Claisen, Ann., 442,221 (1924).
